Clinical applications of intracranial pressure monitoring in traumatic brain injury : report of the Milan consensus conference

Secondary brain injury: Predicting and preventing insults

Mortality or severe disability affects the majority of patients after severe traumatic brain injury (TBI). Adherence to the brain trauma foundation guidelines has overall improved outcomes; however, traditional as well as novel interventions towards intracranial hypertension and secondary brain injury have come under scrutiny after series of negative randomized controlled trials. In fact, it would not be unfair to say there has been no single major breakthrough in the management of severe TBI in the last two decades. One plausible hypothesis for the aforementioned failures is that by the time treatment is initiated for neuroprotection, or physiologic optimization, irreversible brain injury has already set in. We, and others, have recently developed predictive models based on machine learning from continuous time series of intracranial pressure and partial brain tissue oxygenation. These models provide accurate predictions of physiologic crises events in a timely fashion, offering the opportunity for an earlier application of targeted interventions. In this article, we review the rationale for prediction, discuss available predictive models with examples, and offer suggestions for their future prospective testing in conjunction with preventive clinical algorithms. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury".

Intracranial pressure management in patients with traumatic brain injury: an update

PURPOSE OF REVIEW

Intracranial pressure (ICP) monitoring and treatment is central in the management of traumatic brain injury. Despite 4 decades of clinical use, several aspects remain controversial, including the indications for ICP and treatment options.

RECENT FINDINGS

Two major trials tested surgical decompression and mild hypothermia as treatments for high ICP. Both were rigorous, randomized, multicenter studies, with different designs. Decompression was tested for ICP refractory to conventional treatment, whereas hypothermia was offered as an alternative to conventional medical therapy. Decompression reduced mortality, but at the expense of more disability. The hypothermia trial was stopped because of a worse outcome in the treated arm. Indications for ICP monitoring have been reviewed and new international guidelines issued. New contributions published in 2016 have dealt with computerized analysis for predicting ICP crises; noninvasive or innovative methods for measuring ICP; reassessment of standard therapeutic interventions, such as hypertonic solutions and the level of intensity of ICP therapy.

SUMMARY

Aggressive strategies for ICP control, like surgical decompression or hypothermia, carefully tested, have controversial effects on outcome. Several articles have made worthwhile contributions to important clinical issues, but with no real breakthroughs.

Intracranial pressure in patients undergoing decompressive craniectomy: new perspective on thresholds

OBJECTIVE

Decompressive craniectomy (DC) is an established part of treatment in patients suffering from malignant infarction of the middle cerebral artery (MCA) or traumatic brain injury (TBI). However, no clear evidence for intracranial pressure (ICP)-guided therapy after DC exists. The lack of this evidence might be due to the frequently used, but simplified threshold for ICP of 20 mm Hg, which determines further therapy. Therefore, the objective of this study was to evaluate this threshold's accuracy and to investigate the course of ICP values with respect to neurological outcome.

METHODS

Data on clinical characteristics and parameters of the ICP course on the intensive care unit were collected retrospectively in 102 patients who underwent DC between December 2007 and April 2014 at the authors' institution. The postoperative ICP course in the first 168 hours was recorded and analyzed. From these findings, ICP thresholds discriminating favorable from unfavorable outcome were calculated using conditional inference tree analysis. Additionally, survival analysis was performed using the Kaplan-Meier method. Prognostic factors were assessed via univariate analysis and multivariate logistic regression. Favorable outcome was defined as a score of 0–4 on the modified Rankin Scale.

RESULTS

Multivariate logistic regression revealed that anisocoria, diagnosis, and ICP values differed significantly between the outcome groups. ICP values in the favorable and unfavorable outcome groups differed significantly (p < 0.001), while the mean ICP of both groups lay below the limit of 20 mm Hg (17.5 and 11.5 mm Hg, respectively). These findings were reproduced when analyzing the underlying pathologies of TBI and MCA infarction separately. Based on these findings, optimized time-dependent threshold values were calculated and found to be between 10 and 17 mm Hg. These values significantly distinguished favorable from unfavorable outcome and predicted 30-day mortality (p < 0.001).

CONCLUSIONS

This study systematically evaluated ICP levels in a long-term analysis after DC and provides new, surprisingly low, time-dependent ICP thresholds for these patients. Future trials investigating the benefit of ICP-guided therapy should take these thresholds into consideration and validate them in further patient cohorts.

Management of severe traumatic brain injury (first 24hours)

The latest French Guidelines for the management in the first 24hours of patients with severe traumatic brain injury (TBI) were published in 1998. Due to recent changes (intracerebral monitoring, cerebral perfusion pressure management, treatment of raised intracranial pressure), an update was required. Our objective has been to specify the significant developments since 1998. These guidelines were conducted by a group of experts for the French Society of Anesthesia and Intensive Care Medicine (Société francaise d'anesthésie et de réanimation [SFAR]) in partnership with the Association de neuro-anesthésie-réanimation de langue française (ANARLF), The French Society of Emergency Medicine (Société française de médecine d'urgence (SFMU), the Société française de neurochirurgie (SFN), the Groupe francophone de réanimation et d'urgences pédiatriques (GFRUP) and the Association des anesthésistes-réanimateurs pédiatriques d'expression française (ADARPEF). The method used to elaborate these guidelines was the Grade^® method. After two Delphi rounds, 32 recommendations were formally developed by the experts focusing on the evaluation the initial severity of traumatic brain injury, the modalities of prehospital management, imaging strategies, indications for neurosurgical interventions, sedation and analgesia, indications and modalities of cerebral monitoring, medical management of raised intracranial pressure, management of multiple trauma with severe traumatic brain injury, detection and prevention of post-traumatic epilepsia, biological homeostasis (osmolarity, glycaemia, adrenal axis) and paediatric specificities.

Current Opportunities for Clinical Monitoring of Axonal Pathology in Traumatic Brain Injury

Traumatic brain injury (TBI) is a multidimensional and highly complex disease commonly resulting in widespread injury to axons, due to rapid inertial acceleration/deceleration forces transmitted to the brain during impact. Axonal injury leads to brain network dysfunction, significantly contributing to cognitive and functional impairments frequently observed in TBI survivors. Diffuse axonal injury (DAI) is a clinical entity suggested by impaired level of consciousness and coma on clinical examination and characterized by widespread injury to the hemispheric white matter tracts, the corpus callosum and the brain stem. The clinical course of DAI is commonly unpredictable and it remains a challenging entity with limited therapeutic options, to date. Although axonal integrity may be disrupted at impact, the majority of axonal pathology evolves over time, resulting from delayed activation of complex intracellular biochemical cascades. Activation of these secondary biochemical pathways may lead to axonal transection, named secondary axotomy, and be responsible for the clinical decline of DAI patients. Advances in the neurocritical care of TBI patients have been achieved by refinements in multimodality monitoring for prevention and early detection of secondary injury factors, which can be applied also to DAI. There is an emerging role for biomarkers in blood, cerebrospinal fluid, and interstitial fluid using microdialysis in the evaluation of axonal injury in TBI. These biomarker studies have assessed various axonal and neuroglial markers as well as inflammatory mediators, such as cytokines and chemokines. Moreover, modern neuroimaging can detect subtle or overt DAI/white matter changes in diffuse TBI patients across all injury severities using magnetic resonance spectroscopy, diffusion tensor imaging, and positron emission tomography. Importantly, serial neuroimaging studies provide evidence for evolving axonal injury. Since axonal injury may be a key risk factor for neurodegeneration and dementias at long-term following TBI, the secondary injury processes may require prolonged monitoring. The aim of the present review is to summarize the clinical short- and long-term monitoring possibilities of axonal injury in TBI. Increased knowledge of the underlying pathophysiology achieved by advanced clinical monitoring raises hope for the development of novel treatment strategies for axonal injury in TBI.

Predicting Intracranial Pressure and Brain Tissue Oxygen Crises in Patients With Severe Traumatic Brain Injury

OBJECTIVES

To develop computer algorithms that can recognize physiologic patterns in traumatic brain injury patients that occur in advance of intracranial pressure and partial brain tissue oxygenation crises. The automated early detection of crisis precursors can provide clinicians with time to intervene in order to prevent or mitigate secondary brain injury.

DESIGN

A retrospective study was conducted from prospectively collected physiologic data. intracranial pressure, and partial brain tissue oxygenation crisis events were defined as intracranial pressure of greater than or equal to 20 mm Hg lasting at least 15 minutes and partial brain tissue oxygenation value of less than 10 mm Hg for at least 10 minutes, respectively. The physiologic data preceding each crisis event were used to identify precursors associated with crisis onset. Multivariate classification models were applied to recorded data in 30-minute epochs of time to predict crises between 15 and 360 minutes in the future.

SETTING

The neurosurgical unit of Ben Taub Hospital (Houston, TX).

SUBJECTS

Our cohort consisted of 817 subjects with severe traumatic brain injury.

MEASUREMENTS AND MAIN RESULTS

Our algorithm can predict the onset of intracranial pressure crises with 30-minute advance warning with an area under the receiver operating characteristic curve of 0.86 using only intracranial pressure measurements and time since last crisis. An analogous algorithm can predict the start of partial brain tissue oxygenation crises with 30-minute advanced warning with an area under the receiver operating characteristic curve of 0.91.

CONCLUSIONS

Our algorithms provide accurate and timely predictions of intracranial hypertension and tissue hypoxia crises in patients with severe traumatic brain injury. Almost all of the information needed to predict the onset of these events is contained within the signal of interest and the time since last crisis.

Intracranial pressure monitoring after primary decompressive craniectomy in traumatic brain injury: a clinical study

BACKGROUND

Intracranial pressure (ICP) monitoring represents an important tool in the management of traumatic brain injury (TBI). Although current information exists regarding ICP monitoring in secondary decompressive craniectomy (DC), little is known after primary DC following emergency hematoma evacuation.

METHODS

Retrospective analysis of prospectively collected data. Inclusion criteria were age ≥18 years and admission to the intensive care unit (ICU) for TBI and ICP monitoring after primary DC. Exclusion criteria were ICU length of stay (LOS) <1 day and pregnancy. Major objectives were: (1) to analyze changes in ICP/cerebral perfusion pressure (CPP) after primary DC, (2) to evaluate the relationship between ICP/CPP and neurological outcome and (3) to characterize and evaluate ICP-driven therapies after DC.

RESULTS

A total of 34 patients were enrolled. Over 308 days of ICP/CPP monitoring, 130 days with at least one episode of intracranial hypertension (26 patients, 76.5%) and 57 days with at least one episode of CPP <60 mmHg (22 patients, 64.7%) were recorded. A statistically significant relationship was discovered between the Glasgow Outcome Scale (GOS) scores and mean post-decompression ICP (p < 0.04) and between GOS and CPP minimum (CPPmin) (p < 0.04). After DC, persisting intracranial hypertension was treated with: barbiturate coma (n = 7, 20.6%), external ventricular drain (EVD) (n = 4, 11.8%), DC diameter widening (n = 1, 2.9%) and removal of newly formed hematomas (n = 3, 8.8%).

CONCLUSION

Intracranial hypertension and/or low CPP occurs frequently after primary DC; their occurence is associated with an unfavorable neurological outcome. ICP monitoring appears useful in guiding therapy after primary DC.

Twenty-Four-Hour Real-Time Continuous Monitoring of Cerebral Edema in Rabbits Based on a Noninvasive and Noncontact System of Magnetic Induction

Cerebral edema is a common disease, secondary to craniocerebral injury, and real-time continuous monitoring of cerebral edema is crucial for treating patients after traumatic brain injury. This work established a noninvasive and noncontact system by monitoring the magnetic induction phase shift (MIPS) which is associated with brain tissue conductivity. Sixteen rabbits (experimental group n = 10, control group, n = 6) were used to perform a 24 h MIPS and intracranial pressure (ICP) simultaneously monitored experimental study. For the experimental group, after the establishment of epidural freeze-induced cerebral edema models, the MIPS presented a downward trend within 24 h, with a change magnitude of −13.1121 ± 2.3953°; the ICP presented an upward trend within 24 h, with a change magnitude of 12–41 mmHg. The ICP was negatively correlated with the MIPS. In the control group, the MIPS change amplitude was −0.87795 ± 1.5146 without obvious changes; the ICP fluctuated only slightly at the initial value of 12 mmHg. MIPS had a more sensitive performance than ICP in the early stage of cerebral edema. These results showed that this system is basically capable of monitoring gradual increases in the cerebral edema solution volume. To some extent, the MIPS has the potential to reflect the ICP changes.

Multimodality Neuromonitoring

The monitoring of systemic and central nervous system physiology is central to the management of patients with neurologic disease in the perioperative and critical care settings. There exists a range of invasive and noninvasive and global and regional monitors of cerebral hemodynamics, oxygenation, metabolism, and electrophysiology that can be used to guide treatment decisions after acute brain injury. With mounting evidence that a single neuromonitor cannot comprehensively detect all instances of cerebral compromise, multimodal neuromonitoring allows an individualized approach to patient management based on monitored physiologic variables rather than a generic one-size-fits-all approach targeting predetermined and often empirical thresholds.

The accuracy of transcranial Doppler in excluding intracranial hypertension following acute brain injury: a multicenter prospective pilot study

BACKGROUND

Untimely diagnosis of intracranial hypertension may lead to delays in therapy and worsening of outcome. Transcranial Doppler (TCD) detects variations in cerebral blood flow velocity which may correlate with intracranial pressure (ICP). We investigated if intracranial hypertension can be accurately excluded through use of TCD.

METHOD

This was a multicenter prospective pilot study in patients with acute brain injury requiring invasive ICP (ICPi) monitoring. ICP estimated with TCD (ICPtcd) was compared with ICPi in three separate time frames: immediately before ICPi placement, immediately after ICPi placement, and 3 hours following ICPi positioning. Sensitivity and specificity, and concordance correlation coefficient between ICPi and ICPtcd were calculated. Receiver operating curve (ROC) and the area under the curve (AUC) analyses were estimated after measurement averaging over time.

RESULTS

A total of 38 patients were enrolled, and of these 12 (31.6%) had at least one episode of intracranial hypertension. One hundred fourteen paired measurements of ICPi and ICPtcd were gathered for analysis. With dichotomized ICPi (≤20 mmHg vs >20 mmHg), the sensitivity of ICPtcd was 100%; all measurements with high ICPi (>20 mmHg) also had a high ICPtcd values. Bland-Altman plot showed an overestimation of 6.2 mmHg (95% CI 5.08-7.30 mmHg) for ICPtcd compared to ICPi. AUC was 96.0% (95% CI 89.8-100%) and the estimated best threshold was at ICPi of 24.8 mmHg corresponding to a sensitivity 100% and a specificity of 91.2%.

CONCLUSIONS

This study provides preliminary evidence that ICPtcd may accurately exclude intracranial hypertension in patients with acute brain injury. Future studies with adequate power are needed to confirm this result.

Management of Intracranial Pressure

PURPOSE OF REVIEW

Intracranial pressure (ICP) can be elevated in traumatic brain injury, large artery acute ischemic stroke, intracranial hemorrhage, intracranial neoplasms, and diffuse cerebral disorders such as meningitis, encephalitis, and acute hepatic failure. Raised ICP is also known as intracranial hypertension and is defined as a sustained ICP of greater than 20 mm Hg.

RECENT FINDINGS

ICP must be measured through an invasive brain catheter, typically an external ventricular catheter that can drain CSF and measure ICP, or through an intraparenchymal ICP probe. Proper recognition of the clinical signs of elevated ICP is essential for timely diagnosis and treatment to prevent cerebral hypoperfusion and possible brain death. Clinical signs of elevated ICP include headache, papilledema, nausea, and vomiting in the early phases, followed by stupor and coma, pupillary changes, hemiparesis or quadriparesis, posturing and respiratory abnormalities, and eventually cardiopulmonary arrest.

SUMMARY

Management of elevated ICP is, in part, dependent on the underlying cause. Medical options for treating elevated ICP include head of bed elevation, IV mannitol, hypertonic saline, transient hyperventilation, barbiturates, and, if ICP remains refractory, sedation, endotracheal intubation, mechanical ventilation, and neuromuscular paralysis. Surgical options include CSF drainage if hydrocephalus is present and decompression of a surgical lesion, such as an intracranial hematoma/large infarct or tumor, if the patient's condition is deemed salvageable. Future research should continue investigating medical and surgical options for the treatment of raised ICP, such as hypothermia, drugs that reduce cerebral edema, and operations aimed at reducing intracranial mass effect.

Surgical Treatment of Traumatic Bifrontal Contusions: When and How?

OBJECTIVE

The study aimed to investigate optimal surgical timing, methods, and clinical efficacy of bifrontal decompression craniotomy (BDC) on traumatic bifrontal contusions (TBC).

METHODS

A retrospective analysis was performed of 98 patients with TBC who underwent BDC of 2510 patients with traumatic brain injury. The operation-timing score was used to determine surgical timing.

RESULTS

Ninety-eight cases (19%) underwent amended BDC. Initial Glasgow Coma Score was 13-15 in 52 cases (61%). Initial computed tomography showed hematoma volumes of 15.1 ± 5.2 mL in 73 cases (74%). Preoperative hematoma (80.2 ± 20.5 mL; P < 0.05) was significantly enlarged. Fluctuation in the surgery-timing curve is timing for surgery. Average operation time was 4.5 ± 3.4 days after admission. Hematoma was totally evacuated and Glasgow Coma Score significantly increased (P < 0.05) in all cases. In the follow-up Glasgow Outcome Score, 79 patients (81%) recovered well.

CONCLUSIONS

TBC progressed gradually and deteriorated rapidly; this should be strictly and dynamically observed, and patients should be operated on in a timely manner. Changing the operation-timing score is the gold standard for surgery. Amended BDC can significantly improve the prognosis of patients.

Advances in Intracranial Pressure Monitoring and Its Significance in Managing Traumatic Brain Injury

Intracranial pressure (ICP) measurements are essential in evaluation and treatment of neurological disorders such as subarachnoid and intracerebral hemorrhage, ischemic stroke, hydrocephalus, meningitis/encephalitis, and traumatic brain injury (TBI). The techniques of ICP monitoring have evolved from invasive to non-invasive-with both limitations and advantages. Some limitations of the invasive methods include short-term monitoring, risk of infection, restricted mobility of the subject, etc. The invasiveness of a method limits the frequency of ICP evaluation in neurological conditions like hydrocephalus, thus hampering the long-term care of patients with compromised ICP. Thus, there has been substantial interest in developing noninvasive techniques for assessment of ICP. Several approaches were reported, although none seem to provide a complete solution due to inaccuracy. ICP measurements are fundamental for immediate care of TBI patients in the acute stages of severe TBI injury. In severe TBI, elevated ICP is associated with mortality or poor clinical outcome. ICP monitoring in conjunction with other neurological monitoring can aid in understanding the pathophysiology of brain damage. This review article presents: (a) the significance of ICP monitoring; (b) ICP monitoring methods (invasive and non-invasive); and (c) the role of ICP monitoring in the management of brain damage, especially TBI.

Routine intracranial pressure monitoring in acute coma

BACKGROUND

We know that the brain damage resulting from traumatic and other insults is not due solely to the direct consequences of the primary injury. A significant and potentially preventable contribution to the overall morbidity arises from secondary hypoxic-ischaemic damage. Brain swelling accompanied by raised intracranial pressure (ICP) prevents adequate cerebral perfusion with well-oxygenated blood.Detection of raised ICP could be useful in alerting clinicians to the need to improve cerebral perfusion, with consequent reductions in brain injury.

OBJECTIVES

To determine whether routine ICP monitoring in severe coma of any cause reduces the risk of all-cause mortality or severe disability at final follow-up.

SEARCH METHODS

We searched the Cochrane Injuries Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OvidSP), EMBASE (OvidSP), CINAHL Plus, ISI Web of Science (SCI-EXPANDED & CPCI-S), clinical trials registries and reference lists. We ran the most recent search on 22 May 2015.

SELECTION CRITERIA

All randomised controlled studies of real-time ICP monitoring by invasive or semi-invasive means in acute coma (traumatic or non-traumatic aetiology) versus clinical care without ICP monitoring (that is, guided only by clinical or radiological inference of the presence of raised ICP).

DATA COLLECTION AND ANALYSIS

Two authors (ET and RF) worked independently to identify the one study that met inclusion criteria. JR and RF independently extracted data and assessed risk of bias. We contacted study authors for additional information, including details of methods and outcome data.

MAIN RESULTS

One randomized controlled trial (RCT) meeting the selection criteria has been identified to date.The included study had 324 participants. We judged risk of bias to be low for all categories except blinding of participants and personnel, which is not feasible for this intervention. There were few missing data, and we analysed all on an intention-to-treat basis.Participants could be 13 years of age or older (mean age of sample 29; range 22 to 44), and all had severe traumatic brain injury, mostly due to traffic incidents. All were receiving care within intensive care units (ICUs) at one of six hospitals in either Bolivia or Ecuador. Investigators followed up 92% of participants for six months or until death. The trial excluded patients with a Glasgow Coma Score (GCS) less than three and fixed dilated pupils on admission on the basis that they had sustained brain injury of an unsalvageable severity.The study compared people managed using either an intracranial monitor or non-invasive monitoring (imaging and clinical examination) to identify potentially harmful raised intracranial pressure. Both study groups used imaging and clinical examination measures.Mortality at six months was 56/144 (39%) in the ICP-monitored group and 67/153 (44%) in the non-invasive group.Unfavourable outcome (defined as death or moderate to severe disability at six months) as assessed by the extended Glasgow Outcome Scale (GOS-E) was 80/144 (56%) in the ICP-monitored group and 93/153 (61%) in the non-invasive group.Six percent of participants in the ICP monitoring group had complications related to the monitoring, none of which met criteria for being a serious adverse event. There were no complications relating to the non-invasive group.Other complications and adverse events were comparable between treatment groups, 70/157 (45%) in the ICP-monitored group and 76/167 (46%) in the non-invasive group.Late mortality in both the monitored and non-invasive groups was high, with 35% of deaths occurring > 14 days after injury. The authors comment that this high late mortality may reflect inadequacies in post-ICU services for disabled survivors requiring specialist rehabilitation care.

AUTHORS' CONCLUSIONS

The data from the single RCT studying the role of routine ICP monitoring in acute traumatic coma fails to provide evidence to support the intervention.Research in this area is complicated by the fact that RCTs necessarily assess the combined impact of measurement of ICP with the clinical management decisions made in light of this data. Future studies will need to assess the added value of ICP data alongside other information from the multimodal monitoring typically performed in intensive care unit settings. Additionally, even within traumatically acquired brain injury (TBI), there is great heterogeneity in mechanisms, distribution, location and magnitude of injury, and studies within more homogeneous subgroups are likely to be more informative.

Pathophysiology and clinical management of moderate and severe traumatic brain injury in the ICU

Moderate and severe traumatic brain injury (TBI) is the leading cause of morbidity and mortality among young individuals in high-income countries. Its pathophysiology is divided into two major phases: the initial neuronal injury (or primary injury) followed by secondary insults (secondary injury). Multimodality monitoring now offers neurointensivists the ability to monitor multiple physiologic parameters that act as surrogates of brain ischemia and hypoxia, the major driving forces behind secondary brain injury. The heterogeneity of the pathophysiology of TBI makes it necessary to take into consideration these interacting physiologic factors when recommending for or against any therapies; it may also account for the failure of all the neuroprotective therapies studied so far. In this review, the authors focus on neuroclinicians and neurointensivists, and discuss the developments in therapeutic strategies aimed at optimizing intracranial pressure and cerebral perfusion pressure, and minimizing cerebral hypoxia. The management of moderate to severe TBI in the intensive care unit is moving away from a pure "threshold-based" treatment approach toward consideration of patient-specific characteristics, including the state of cerebral autoregulation. The authors also include a concise discussion on the management of medical and neurologic complications peculiar to TBI as well as an overview of prognostication.

Systemic, local, and imaging biomarkers of brain injury: more needed, and better use of those already established?

Much progress has been made over the past two decades in the treatment of severe acute brain injury, including traumatic brain injury and subarachnoid hemorrhage, resulting in a higher proportion of patients surviving with better outcomes. This has arisen from a combination of factors. These include improvements in procedures at the scene (pre-hospital) and in the hospital emergency department, advances in neuromonitoring in the intensive care unit, both continuously at the bedside and intermittently in scans, evolution and refinement of protocol-driven therapy for better management of patients, and advances in surgical procedures and rehabilitation. Nevertheless, many patients still experience varying degrees of long-term disabilities post-injury with consequent demands on carers and resources, and there is room for improvement. Biomarkers are a key aspect of neuromonitoring. A broad definition of a biomarker is any observable feature that can be used to inform on the state of the patient, e.g., a molecular species, a feature on a scan, or a monitoring characteristic, e.g., cerebrovascular pressure reactivity index. Biomarkers are usually quantitative measures, which can be utilized in diagnosis and monitoring of response to treatment. They are thus crucial to the development of therapies and may be utilized as surrogate endpoints in Phase II clinical trials. To date, there is no specific drug treatment for acute brain injury, and many seemingly promising agents emerging from pre-clinical animal models have failed in clinical trials. Large Phase III studies of clinical outcomes are costly, consuming time and resources. It is therefore important that adequate Phase II clinical studies with informative surrogate endpoints are performed employing appropriate biomarkers. In this article, we review some of the available systemic, local, and imaging biomarkers and technologies relevant in acute brain injury patients, and highlight gaps in the current state of knowledge.